1. Field of the Invention
The present invention relates to a vehicle air conditioner having a main blower and a sub-blower, which can perform air-conditioning of a plurality of different areas in a passenger compartment by using a single air conditioning unit. More particularly, the present invention relates to a control operation of the main blower and the sub-blower, with an automatic control of the sub-blower.
2. Related Art
There have been proposed various kinds of vehicle air conditioners each of which performs air-conditioning of a plurality of different areas, specifically, a front seat area and a rear seat area in a passenger compartment by using a single air conditioning unit.
For example, in a vehicle air conditioner disclosed in JP-A-9-86138, a front air conditioning unit for air-conditioning a front seat area of a passenger compartment is provided with an additional function for blowing off conditioned air also to a rear seat area of the passenger compartment. Specifically, an inlet portion of a rear face duct is connected to the front air conditioning unit at a position immediately after an evaporator, so that conditioned air (cool air) is blown toward a rear upper side of the passenger compartment from a rear face air outlet provided at an outlet of the rear face duct. Further, an inlet portion of a rear foot duct is connected to the front air conditioning unit at a position immediately downstream of a heater core, so that conditioned air (warm air) is blown toward a rear lower side in the passenger compartment from a rear foot air outlet provided at an outlet of the rear foot duct.
In addition, a rear sub-blower is disposed in a rear face duct in addition to a main blower for blowing air in an air passage of the front air conditioning unit, so that conditioned air is blown to the rear face air outlet by the rear sub blower. When the sub-blower starts air blowing operation toward the rear face duct while the main blower operates, an electrical voltage applied to a driving motor of the main blower is corrected to be increased so that it can prevent an air amount to be blown to the front seat area from being decreased.
In the air conditioner of this document, there is described regarding a voltage correction input to the driving motor of the main blower, that is, an automatic correction of an air amount to be blown to the front seat side. However, the air amount level to be blown to the rear seat area of the passenger compartment is selected by switching a rear vent switch (i.e., rear face amount switch) to 0 position→1 position→2 position→3 position.
When the amount of air blown to the front seat area is changed, the air amount to be blown to the rear seat area of the passenger compartment is also changed in accordance with a change of the air blowing amount to the front seat area. Therefore, in order to remove a change of the rear air-blowing amount due to a change of the front air-blowing amount, it is necessary to frequently operate the rear vent switch.
Further, because cold air immediately after the evaporator of the front air conditioning unit is blown to the rear upper side of the passenger compartment through the rear face duct, the temperature of air blown to the rear upper side cannot be adjusted. In addition, because the sub-blower is arranged to blow air only toward the rear upper side, air blowing operation to the rear lower side of the passenger compartment is performed by using the main blower. Generally, a rear foot duct is a slender duct, so air flow resistance (pressure loss) in a rear foot passage becomes greatly larger than that in a front foot passage. As a result, an air amount to be blown to the rear lower side becomes smaller, and a heating shortage may be caused in the rear seat area of the passenger compartment.
The above-described technique of the related art has been described in a case where the front seat area and the rear seat area in the passenger compartment are air-conditioned by using the single front air conditioning unit. However, there is the same problem also in a case where a front area and a passenger's seat in the passenger compartment are air-conditioned by using the single front air conditioning unit, because air flow resistance in a seat-side air passage becomes extremely large as compared with the air flow resistance in the front air passage.